Virtual endoscopy, also known as Computer Tomography (CT) endoscopy is a non-invasive diagnostic procedure allowing the inspection of inner and outer surfaces of anatomical structures in the human body. Recently, such procedure has been used to investigate hollow organs such as the colon as suggested by U.S. Pat. No. 6,694,163 & and U.S. Pat. No. 5,891,030, during colorectal cancer screening. This procedure is known as virtual colonoscopy or CT colonoscopy.
Originally, CT colonoscopy mimicked Optical Colonoscopy by creating a virtual environment representing a 3D view of the inner part of the colon as detailed in U.S. Pat. No. 5,782,762, involving a perspective rendering of the 3D environment. However, it mimicked as well the very limitation of optical colonoscopy, that is being blind to areas located out-of the reach of optical rays, such as behind haustral folds or located between deep folds.
Thus, new techniques emerged to increase the amount of colonic mucosa visualized through a virtual camera, amongst which (1) flat colon techniques detailed in U.S. Pat. No. 5,891,030 [030], (2) cube view detailed in U.S. Pat. No. 6,947,039 (hereinafter '039) shown in FIG. 1a, (3) panoramic projection detailed in U.S. Pat. No. 7,609,910 (hereinafter '910) shown in FIGS. 1b and 1c, (4) unfolded colon projection detailed in US Patent Application 2011/0116692 (hereinafter '692) and more recently (5) object diameter-specific cylindrical projection techniques limiting the distortion of the colon inner section as detailed in US Patent Application 2010/0142788 (hereinafter '788).
Techniques detailed in '030, '692 & '788 have a common limitation, that is a paradigm shift related to the human perception of objects from perspective 3D projections to 2D projections. These techniques introduce visual distortion in shapes, that requires observers to re-learn how to interpret the information, and eventually that may negatively impact the colonic mucosa evaluation. In addition, '692 and '788 aim at reducing these artifacts, but require the evaluation of a limited section of the colon. This leads to two limitations which are an increased reviewing time, and a decrease visual exposition to lesions as opposed to longer exposition in traditional perspective projections.
Furthermore, technique detailed in '039 has an inherent drawback which is the constant exposition of front and back projections, similar to always watching a rear-mirror while driving. In addition, and because only cube views are involved to represent a complete 360 environment, some objects can be partially present in multiple edges of different cube views. These two drawbacks are a clear limitation to the technique leading to a non efficient clinical reading paradigm.
An evolution of '039 to overcome the split-view of edge objects, and the information overflow, is detailed in '910. The technique involves distorting some of the cube views and assembles them around the Front-view, while removing the Back-view. Intrinsically, and although '039 proposes two different layouts, the distortion are non-homogeneous in the image along radial image lines starting at the center of the Front-view; the distortion implies that an identical object will be seen differently depending on where it is positioned in the “distorted assembled view”, creating additional artifacts for the observer. Furthermore, the cube-view distortion does not provide a practical alternative solution in case colonic folds are really compact in a specific region as the limited and non-linearly distorted field-of-view will remain blind to most of the information. Finally, '039 requires a mapping process that either delete, interpolate or somehow alter the original information in order to have it fit into the final assembled space, increasing processing time and intrinsically altering the clinical information.
There is a need a method and apparatus that will overcome at least one of the above-identified drawbacks.
Features of the invention will be apparent from review of the disclosure, drawings and description of the invention below.